The proposed project is designed to provide data necessary to help stop the spread of HIV infection among all intravenous drug users in and out of treatment. It is crucial that the subjects we study accurately represent the population of IVDUs at risk for HIV infection. In particular, we need to insure adequate representation of women and minorities among whom the virus may be more rapidly spreading. This application proposes to extend our current study and add new subjects. We expect that the new subject group will be demographically similar to our existing sample in which we have 30% women, 60% African American, 10% Hispanic, and 30% Caucasian. We have worked very hard to retain all subjects without regard to gender or racial characteristics. We have designed our recruitment procedures so that our new sample will include men and women, Caucasians, African Americans, and Hispanics. Certainly no potential subject will be excluded due to their gender or race. The research is based in a racially and ethnically diverse community and we will make every effort to insure that our sample fully reflects that diversity. We have proposed to recruit a new cohort of subject which should add sufficient numbers to our existing cohort to strengthen our findings and increase the power of our analyses for various gender and racial subgroups. Native Americans and Asian/Pacific Islanders are not excluded from the research but are not sufficiently represented among IVDUs in this area to provide adequate numbers for statistical analyses.